This invention is directed to a magnetic shielding plate for a step motor in an electronic wristwatch, and in particular to the use of a magnetic shielding plate to surround the coil assembly of a step motor in an electronic wristwatch for preventing the operation of the step motor from being affected by external magnetic fields.
In recent years, the popularity of quartz crystal electronic wristwatches has been due, in large measure, to two not unrelated developments in such wristwatches. The first development involved the increased accuracy that is obtained by utilizing quartz crystal vibrators capable of oscillating at extremely high frequencies as a time standard. The second development is directed to the gradual reduction in the thickness of the electronic movement in the wristwatch thereby providing electronic wristwatches that are beginning to approach the thin profile of mechanical wristwatches. Quartz crystal electronic wristwatches have now been commercialized with electronic movements having a thickness on the order of 4 mm. Accordingly, a further reduction in the thickness of an electronic timepiece movement to 3 mm or less by maximizing the use of a magnetic shielding plate is desired.